Accurate location of the June 24, 2012 Ninglang- Yanyuan MS5.7 earthquake
-
摘要: 采用双差定位方法对2012年6月24日宁蒗-盐源MS5.7地震主震及其余震序列进行了重新定位. 首先采用时间域互相关技术对波形数据进行处理, 获得高精度的事件对走时差; 然后分别使用目录数据、 波形互相关数据和目录数据+波形互相关数据等3种不同的数据组合, 对宁蒗-盐源MS5.7地震主震及其余震序列进行重新定位. 3种数据组合的主震定位结果、 参与重定位的地震事件数、 最终被定位的地震事件数及重定位结果标准差等对比结果表明, 同时使用目录数据和波形互相关数据所获得的重定位结果最佳. 重定位结果显示, 宁蒗-盐源MS5.7地震主震的震中位置为(27.790°N、 100.707°E), 震源深度为10.4 km, 发震时刻为北京时间2012年6月24日15时59分32.74秒. 本文结果表明, 震源区附近NW走向的永宁断裂为宁蒗-盐源MS5.7地震的发震构造.
-
关键词:
- 宁蒗-盐源MS5.7地震 /
- 双差定位 /
- 波形互相关 /
- 永宁断裂
Abstract: This paper relocated the 24 June 2012 Ninglang-Yanyuan MS5.7 earthquake and its aftershock sequence with double-difference earthquake location algorithm. Firstly, we used the cross-correlation technique in time domain to deal with waveform data and got high accuracy differential travel-time data of event pairs. And then we used three different data sets, which are catalog data, waveform cross-correlation data, and catalog data plus waveform cross-correlation data, as the initial data to relocate the Ninglang-Yanyuan earthquake sequence. Comparing the location of main shock, the number of events involved in relocation, the number of events relocated and relocation error for the three data sets, it is suggested that the relocation result of the third data set is the best. The result shows that the original time of the main shock is 15:59:32.74 (Beijing Time) on 24 June 2012, hypocenter location is (27.790°N, 100.707°E), and the focal depth is 10.4 km. Our research also shows that the nearby Yong-ning fault is the seismogenic structure of Ninglang-Yanyuan MS5.7 earthquake sequence. -
-
图 3 宁蒗-盐源地震序列的初始定位结果
(a) 震中分布图; (b) 所有地震在AA′剖面上的投影; (c) 所有地震在BB′剖面上的投影
Figure 3. Initial location of the Ninglang-Yanyuan earthquake sequence
(a) The epicentraldistribution, where the profile AA′ is perpendicular to the profile BB′;(b) Projection of all the earthquakes along the profile AA′;(c) Projection of all the earthquakes along the profile BB′
图 5 宁蒗-盐源地震序列单独使用地震目录数据的重定位结果
(a) 震中分布图; (b) 所有地震在AA′剖面上的投影; (c) 所有地震在BB′剖面上的投影
Figure 5. Relocation result ofthe 2012 Ninglang-Yanyuan earthquake sequence based on catalog data
(a) The epicentraldistribution, where the profile AA′ is perpendicular to the profile BB′;(b) Projection of all the earthquakes along the profile AA′;(c) Projection of all the earthquakes along the profile BB′
图 6 宁蒗-盐源地震序列单独使用波形互相关数据的重定位结果
(a) 震中分布图; (b) 所有地震在AA′剖面上的投影; (c) 所有地震在BB′剖面上的投影
Figure 6. Relocation result of the 2012 Ninglang-Yanyuanearthquake sequence based on cross-correlation waveform data
(a) The epicentraldistribution, where the profile AA′ is perpendicular to the profile BB′;(b) Projection of all the earthquakes along the profile AA′;(c) Projection of all the earthquakes along the profile BB′
图 7 宁蒗-盐源地震序列同时使用地震目录和波形互相关数据的重定位结果
(a) 震中分布图; (b) 所有地震在AA′剖面上的投影; (c) 所有地震在BB′剖面上的投影
Figure 7. Relocation result of the 2012 Ninglang-Yanyuan earthquake sequence based on catalog data and cross-correlation waveform data
(a) The epicentraldistribution, where the profile AA′ is perpendicular to the profile BB′;(b) Projection of all the earthquakes along the profile AA′;(c) Projection of all the earthquakes along the profile BB′
表 1 宁蒗地区速度模型
Table 1 Velocity model of Ninglang area
地壳厚度/km v P/(km·s -1) v S/(km·s -1) 0—1 4.60 2.659 1—11 6.35 3.671 11—25 6.40 3.699 25—35.5 6.55 3.786 35.5—56 7.45 4.306 56—74 8.15 4.711 >74 8.50 4.913 表 2 不同机构得到的宁蒗-盐源地震主震定位结果(引自胡朝忠等, 2012)
Table 2 Location results ofthe 2012 Ninglang-Yanyuan main shockfrom different institutions (after Hu et al, 2012)
机构 北纬/° 东经/° 震源深度/km 中国地震台网 27.7 100.7 11 USGS 27.767 100.768 13 哈佛大学 27.66 100.83 12 表 3 本文得到的宁蒗-盐源地震主震定位结果
Table 3 Location result of the 2012 Ninglang- Yanyuan main shock obtained bythis study
数据类型 北纬/° 东经/° 深度/km 原始定位结果 27.778 100.664 7.0 目录数据 27.761 100.685 8.9 波形互相关数据 27.754 100.696 10.5 目录数据+波形 27.790 100.707 10.4 互相关数据 表 4 本文得到的宁蒗-盐源地震序列定位误差
Table 4 Analysis on location errors of the 2012 Ninglang-Yanyuan earthquake sequence obtained in this study
数据组合 成群
地震数重定位
地震数EW向平均
误差/kmNS向平均
误差/km深度平均
误差/km发震时刻
平均误差/s目录数据 415 334 0.25 0.42 0.61 0.059 波形互相关数据 334 221 0.16 0.39 0.61 0.036 目录数据+波形 122 111 0.13 0.07 0.19 0.018 互相关数据 表 5 基于相同样本得到的宁蒗-盐源地震序列的定位误差
Table 5 Location errors of the 2012 Ninglang-Yanyuan earthquake sequence based onthesame samples
数据组合 成群
地震数重定位
地震数EW向平均
误差/kmNS向平均
误差/km深度平均
误差/km发震时刻
平均误差/s目录数据 122 106 0.48 0.32 0.80 0.060 波形互相关数据 122 110 0.04 0.02 0.06 0.005 目录数据+波形 122 111 0.13 0.07 0.19 0.018 互相关数据 -